The fundamental idea of millenarianism, as understood by Christian writers, may be set forth as follows: At the end of time Christ will return in all His splendour to gather together the just, to annihilate hostile powers, and to found a glorious kingdom on earth for the enjoyment of the highest spiritual and material blessings; He Himself will reign as its king, and all the just, including the saints recalled to life, will participate in it. At the close of this kingdom the saints will enter heaven with Christ, while the wicked, who have also been resuscitated, will be condemned to eternal damnation. The duration of this glorious reign of Christ and His saints on earth, is frequently given as one thousand years. Hence it is commonly known as the "millennium", while the belief in the future realization of the kingdom is called "millenarianism" (or "chiliasm", from the Greek chilia, scil. ete).

This term of one thousand years, however, is by no means an essential element of the millennium as conceived by its adherents. The extent, details of the realization, conditions, the place, of the millennium were variously described. Essential are the following points:

the early return of Christ in all His power and glory,

the establishment of an earthly kingdom with the just,

the resuscitation of the deceased saints and their participation in the glorious reign,

the destruction of the powers hostile to God, and,

at the end of the kingdom, the universal resurrection with the final judgment, after which the just will enter heaven, while the wicked will be consigned to the eternal fire of hell.

The roots of the belief in a glorious kingdom, partly natural, partly supernatural, are found in the hopes of the Jews for a temporal Messiah and in the Jewish apocalyptic. Under the galling pressure of their political circumstances the expectation of a Messiah who would free the people of God had in the Jewish mind, assumed a character that was to a great extent earthly; the Jews longed above all for a saviour who would free them from their oppressors and restore the former splendour of Israel. These expectations generally included the belief that Jehovah would conquer all powers hostile to Himself and to His chosen people, and that He would set up a final, glorious kingdom of Israel. The apocalyptic books, principally the book of Henoch and the fourth book of Esdras, indicate various details of the arrival of the Messiah, the defeat of the nations hostile to Israel, and the union of all the Israelites in the Messianic kingdom followed by the renovation of the world and the universal resurrection.

The natural and the supernatural are mingled in this conception of a Messianic kingdom as the closing act of the world's history. The Jewish hopes of a Messiah, and the descriptions of apocalyptic writers were blended; it was between the close of the present world-order and the commencement of the new that this sublime kingdom of the chosen people was to find its place. That many details of these conceptions should remain indistinct and confused was but natural, but the Messianic kingdom is always pictured as something miraculous, though the colours are at times earthly and sensuous. The evangelical accounts clearly prove how fervently the Jews at the time of Christ expected an earthly Messianic kingdom, but the Saviour came to proclaim the spiritual kingdom of God for the deliverance of man from his sins and for his sanctification, a kingdom which actually began with His birth. There is no trace of chiliasm to be found in the Gospels or in the Epistles of St. Paul; everything moves in the spiritual and religious sphere; even the descriptions of the end of the world and of the last judgment bear this stamp. The victory over the symbolical beast (the enemy of God and of the saints) and over Antichrist, as well as the triumph of Christ and His saints, are described in the Apocalypse of St. John (Apoc., 20-21), in pictures that resemble those of the Jewish apocalyptic writers, especially of Daniel and Henoch. Satan is chained in the abyss for a thousand years, the martyrs and the just rise from the dead and share in the priesthood and kingship of Christ. Though it is difficult to focus sharply the pictures used in the Apocalypse and the things expressed by them, yet there can be no doubt that the whole description refers to the spiritual combat between Christ and the Church on the one hand and the malignant powers of hell and the world on the other. Nevertheless, a large number of Christians of the post-Apostolic era, particularly in Asia Minor, yielded so far to Jewish apocalyptic as to put a literal meaning into these descriptions of St. John's Apocalypse; the result was that millenarianism spread and gained staunch advocates not only among the heretics but among the Catholic Christians as well.

One of the heretics, the Gnostic Cerinthus, who flourished towards the end of the first century, proclaimed a splendid kingdom of Christ on earth which He would establish with the risen saints upon His second advent, and pictured the pleasures of this one thousand years in gross, sensual colours (Caius in Eusebius, "Hist. Eccl.", III, 28; Dionysius Alex. in Eusebius, ibid., VII, 25). Later among Catholics, Bishop Papias of Hierapolis, a disciple of St. John, appeared as an advocate of millenarianism. He claimed to have received his doctrine from contemporaries of the Apostles, and Irenaeus narrates that other "Presbyteri", who had seen and heard the disciple John, learned from him the belief in millenarianism as part of the Lord's doctrine. According to Eusebius (Hist. Eccl., 111, 39) Papias in his book asserted that the resurrection of the dead would be followed by one thousand years of a visible glorious earthly kingdom of Christ, and according to Irenaeus (Adv. Haereses, V, 33), he taught that the saints too would enjoy a superabundance of earthly pleasures. There will be days in which vines will grow, each with 10,000 branches, and on each branch 10,000 twigs, and on each twig 10,000 shoots, and in each shoot 10,000 clusters, and on each cluster 10,000 grapes, and each grape will produce 216 gallons of wine etc.

Millenarian ideas are found by most commentators in the Epistle of St. Barnabas, in the passage treating of the Jewish sabbath; for the resting of God on the seventh day after the creation is explained in the following manner. After the Son of God has come and put an end to the era of the wicked and judged them, and after the sun, the moon, and the stars have been changed, then He will rest in glory on the seventh day. The author had premised, if it is said that God created all things in six days, this means that God will complete all things in six millenniums, for one day represents one thousand years. It is certain that the writer advocates the tenet of a re-formation of the world through the second advent of Christ, but it is not clear from the indications whether the author of the letter was a millenarian in the strict sense of the word. St. Irenaeus of Lyons, a native of Asia Minor, influenced by the companions of St. Polycarp, adopted millenarian ideas, discussing and defending them in his works against the Gnostics (Adv. Haereses, V, 32). He developed this doctrine mainly in opposition to the Gnostics, who rejected all hopes of the Christians in a happy future life, and discerned in the glorious kingdom of Christ on earth principally the prelude to the final, spiritual kingdom of God, the realm of eternal bliss. St. Justin of Rome, the martyr, opposes to the Jews in his Dialogue with Tryphon (ch. 80-1) the tenet of a millennium and asserts that he and the Christians whose belief is correct in every point know that there will be a resurrection of the body and that the newly built and enlarged Jerusalem will last for the space of a thousand years, but he adds that there are many who, though adhering to the pure and pious teachings of Christ, do not believe in it. A witness for the continued belief in millenarianism in the province of Asia is St. Melito, Bishop of Sardes in the second century. He develops the same train of thought as did St. Irenaeus.

The Montanistic movement had its origin in Asia Minor. The expectation of an early advent of the celestial Jerusalem upon earth, which, it was thought, would appear in Phrygia, was intimately joined in the minds of the Montanists with the idea of the millennium. Tertullian, the protagonist of Montanism, expounds the doctrine (in his work now lost, "De Spe Fidelium" and in "Adv. Marcionem", IV) that at the end of time the great Kingdom of promise, the new Jerusalem, would be established and last for the space of one thousand years. All these millenarian authors appeal to various passages in the prophetic books of the Old Testament, to a few passages in the Letters of St. Paul and to the Apocalypse of St. John. Though millenarianism had found numerous adherents among the Christians and had been upheld by several ecclesiastical theologians, neither in the post-Apostolic period nor in the course of the second century, does it appear as a universal doctrine of the Church or as a part of the Apostolic tradition. The primitive Apostolic symbol mentions indeed the resurrection of the body and the return of Christ to judge the living and the dead, but it says not a word of the millennium. It was the second century that produced not only defenders of the millennium but pronounced adversaries of the chiliastic ideas. Gnosticism rejected millenarianism. In Asia Minor, the principal seat of millenarian teachings, the so-called Alogi rose up against millenarianism as well as against Montanism, but they went too far in their opposition, rejecting not only the Apocalypse of St. John, alleging Cerinthus as its author, but his Gospel also. The opposition to millenarianism became more general towards the end of the second century, going hand in hand with the struggle against Montanism. The Roman presbyter Caius (end of the second and beginning of the third century) attacked the millenarians. On the other hand, Hippolytus of Rome defended them and attempted a proof, basing his arguments on the allegorical explanation of the six days of creation as six thousand years, as he had been taught by tradition.

The most powerful adversary of millenarianism was Origen of Alexandria. In view of the Neo-Platonism on which his doctrines were founded and of his spiritual-allegorical method of explaining the Holy Scriptures, he could not side with the millenarians. He combatted them expressly, and, owing to the great influence which his writings exerted on ecclesiastical theology especially in Oriental countries, millenarianism gradually disappeared from the idea of Oriental Christians. Only a few later advocates are known to us, principally theological adversaries of Origen. About the middle of the third century, Nepos, bishop in Egypt, who entered the lists against the allegorism of Origen, also propounded millenarian ideas and gained some adherents in the vicinity of Arsino . A schism threatened; but the prudent and moderate policy of Dionysius, Bishop of Alexandria, preserved unity; the chiliasts abandoned their views (Eusebius "Hist. Eccl.", VII, 14). Egypt seems to have harboured adherents of millenarianism in still later times Methodius, Bishop of Olympus, one of the principal opponents of Origen at the beginning of the fourth century, upheld chiliasm in his Symposion (IX, 1, 5). In the second half of the fourth century, these doctrines found their last defender in Apollinaris, Bishop of Laodicea and founder of Apollinarism (q.v.). His writings on this subject, have been lost; but St. Basil of Caesarea (Epist. CCLXIII, 4), Epiphanius (Haeres. LXX, 36) and Jerome (In Isai. XVIII) testify to his having been a chiliast. Jerome also adds that many Christians of that time shared the same beliefs; but after that millenarianism found no outspoken champion among the theologians of the Greek Church.

In the West, the millenarian expectations of a glorious kingdom of Christ and His just, found adherents for a long time. The poet Commodian (Instructiones, 41, 42, 44) as well as Lactantius (Institutiones, VII) proclaim the millennial realm and describe its splendour, partly drawing on the earlier chiliasts and the Sybilline prophecies, partly borrowing their colours from the "golden age" of the pagan poets; but the idea of the six thousand years for the duration of the world is ever conspicuous. Victorinus of Pettau also was a millenarian though in the extant copy of his commentary on the Apocalypse no allusions to it can be detected. St. Jerome, himself a decided opponent of the millenial ideas, brands Sulpicius Severus as adhering to them, but in the writings of this author in their present form nothing can be found to support this charge. St. Ambrose indeed teaches a twofold resurrection, but millenarian doctrines do not stand out clearly. On the other hand; St. Augustine was for a time, as he himself testifies (De Civitate Dei, XX, 7), a pronounced champion of millenarianism; but he places the millennium after the universal resurrection and regards it in a more spiritual light (Sermo, CCLIX). When, however, he accepted the doctrine of only one universal resurrection and a final judgment immediately following, he could no longer cling to the principal tenet of early chiliasm. St. Augustine finally held to the conviction that there will be no millennium. The struggle between Christ and His saints on the one hand and the wicked world and Satan on the other, is waged in the Church on earth; so the great Doctor describes it in his work De Civitate Dei. In the same book he gives us an allegorical explanation of Chapter 20 of the Apocalypse. The first resurrection, of which this chapter treats, he tells us, refers to the spiritual rebirth in baptism; the sabbath of one thousand years after the six thousand years of history is the whole of eternal life — or in other words, the number one thousand is intended to express perfection, and the last space of one thousand years must be understood as referring to the end of the world; at all events, the kingdom of Christ, of which the Apocalypse speaks, can only be applied to the Church (De Civitate Dei, XX 5-7). This explanation of the illustrious Doctor was adopted by succeeding Western theologians, and millenarianism in its earlier shape no longer received support. Cerinthus and the Ebionites are mentioned in later writings against the heretics as defenders of the millennium, it is true, but as cut-off from the Church. Moreover, the attitude of the Church towards the secular power had undergone a change with closer connection between her and the Roman empire. There is no doubt that this turn of events did much towards weaning the Christians from the old millenarianism, which during the time of persecution had been the expression of their hopes that Christ would soon reappear and overthrow the foes of His elect. Chiliastic views disappeared all the more rapidly, because, as was remarked above, in spite of their wide diffusion even among sincere Christians, and in spite of their defence by prominent Fathers of the early Church, millenarianism was never held in the universal Church as an article of faith based on Apostolic traditions.

The Middle Ages were never tainted with millenarianism; it was foreign both to the theology of that period and to the religious ideas of the people. The fantastic views of the apocalyptic writers (Joachim of Floris, the Franciscan-Spirituals, the Apostolici), referred only to a particular form of spiritual renovation of the Church, but did not include a second advent of Christ. The "emperor myths," which prophesied the establishment of a happy, universal kingdom by the great emperor of the future, contain indeed descriptions that remind one of the ancient Sybilline and millenarian writings, but an essential trait is again missing, the return of Christ and the connection of the blissful reign with the resurrection of the just. Hence the millennium proper is unknown to them. The Protestantism of the sixteenth century ushered in a new epoch of millenarian doctrines. Protestant fanatics of the earlier years, particularly the Anabaptists, believed in a new, golden age under the sceptre of Christ, after the overthrow of the papacy and secular empires. In 1534 the Anabaptists set up in Münster (Westphalia) the new Kingdom of Zion, which advocated sharing property and women in common, as a prelude to the new kingdom of Christ. Their excesses were opposed and their millenarianism disowned by both the Augsberg (art. 17) and the Helvetian Confession (ch. 11), so that it found no admission into the Lutheran and Reformed theologies. Nevertheless, the seventeenth and eighteenth centuries produced new apocalyptic fanatics and mystics who expected the millennium in one form or another: in Germany, the Bohemian and Moravian Brethren (Comenius); in France, Pierre Jurien (L'Accomplissement des Propheties, 1686); in England at the time of Cromwell, the Independents and Jane Leade. A new phase in the development of millenarian views among the Protestants commenced with Pietism. One of the chief champions of the millennium in Germany was I.A. Bengel and his disciple Crusius, who were afterwards joined by Rothe, Volch, Thiersch, Lange and others. Protestants from Wurtemberg emigrated to Palestine (Temple Communities) in order to be closer to Christ at His second advent. Certain fantastical sects of England and North America, such as the Irvingites, Mormons, Adventists, adopted both apocalyptic and millenarian views, expecting the return of Christ and the establishment of His kingdom at an early date. Some Catholic theologians of the nineteenth century championed a moderate, modified millenarianism, especially in connection with their explanations of the Apocalypse; as Pagani (The End of the World, 1856), Schneider (Die chiliastische Doktrin, 1859), Rohling (Erklärung der Apokalypse des hl. lohannes, 1895; Auf nach Sion, 1901), Rougeyron Chabauty (Avenir de l'Eglise catholique selon le Plan Divin, 1890).